Scientific consensus? *snort*
I don't think that's true at all. In universities, for instance, tablet + stylus are widely used for delivering lectures and as a practical replacement for the somewhat impractical interactive whiteboards ("smartboards") that everyone was hyping a few years back. In fact I think in any situation where you want to do handwriting on your device a stylus is the best option (for instance someone above mentioned equation input).
Reasons pen input is not a gimick:
1. Truly mobile scenarios such as your doctor taking notes at your bedside require one handed, fast input, which you won't get from a keyboard, virtual or otherwise.
2. True note taking requires the ability to jot notes anywhere, to be able to draw, etc. You can't beat pen input when brain storming.
3. Drawing and CAD applications simply aren't going to work well with a fat finger.
4. Accessibility concerns often means that pen input is preferred or even necessary. Ask someone with bad arthritis (a large segment of the consumer population) if they'd rather use a keyboard, touch screen or stylus.
Jobs was simply wrong. If you require a pen, you're failing, but if you don't have good pen support your failing even worse. With the keyboard and pen these devices aren't just consumption devices, and as such they are far more appealing to me.